Dual Targeting of PTP1B and Aldose Reductase with Marine Drug Phosphoeleganin: A Promising Strategy for Treatment of Type 2 Diabetes

The Mediterranean Sea on the Bench: Unveiling the Marine Invertebrate Sidnyum elegans as a Source of Novel Promising Therapeutic Tools Against Triple-Negative Breast Cancer

This study aims to unveil the marine invertebrate Sidnyum elegans, a Mediterranean ascidian, as a natural resource for the early development of new treatments for triple-negative breast cancer (TNBC). Nine different fractions obtained via medium-pressure liquid chromatography (MPLC) of the butanol-soluble material of the ascidian were evaluated in proliferating MDA-MB-231 cells in a range of 10-50 µg/mL. Among them, the SEB-5 fraction was found to be the most effective in reducing cell proliferation and concomitantly inducing apoptosis, revealed via MTT assay and FACS analysis using Annexin V/PI dual staining. Furthermore, we investigated the effect of this fraction on cell cycle phases, revealing that SEB-5 can arrest the cells in the G0/G1 phase. This latter effect was then confirmed via transcriptomic analysis, showing that treatment with SEB-5 reduced the expression of cyclinB1, CDC25a, and CDK1. Finally, to evaluate the potential antimetastatic effect of SEB-5, a wound-healing assay was performed showing the ability of SEB-5 to reduce MDA-MB-231 cell migration. The chemical characterization of SEB-5 components was performed using liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS/MS) and nuclear magnetic resonance (NMR) spectroscopy. This analysis revealed the presence of a terpenoid and polyketide-like compounds, including the alkyl sulfate 1 and phosphoeleganin 2, along with three novel phosphoeleganin-related products 3-5.

Investigating the Catalytic Site of Human 15-Lipoxygenase-1 via Marine Natural Products

Human 15-lipoxygenase-1 (15-LOX-1) is a key enzyme that possesses an important role in (neuro)inflammatory diseases. The pocket of the enzyme plays the role of a chiral catalyst, and therefore chirality could be an important component for the design of effective enzyme inhibitors. To advance our knowledge on this concept, we developed a library of the identified chiral 15-LOX-1 inhibitors and applied cheminformatic tools. Our analysis highlighted specific structural elements, which we integrated them in small molecules, and employed them as "smart" tools to effectively navigate the chemical space of previously unexplored regions. To this purpose, we utilized the marine derived natural product phosphoeleganin (PE) among with a small library of synthetic fragment derivatives, including a certain degree of stereochemical diversity. Enzyme inhibition/kinetic and molecular modelling studies has been performed in order to characterize structurally novel PE-based inhibitors, which proved to present a different type of inhibition with low micromolar potency, according to their structural features. We demonstrate that different warheads work as anchor, and either guide specific stereochemistry, or causing a time-depended inhibition. Finally, we prove that the positioning of the chiral substituents or/and the favorable stereochemistry can be crucial, as it can lead from active to completely inactive compounds.

Marine-Derived Phosphoeleganin and Its Semisynthetic Derivative Decrease IL6 Levels and Improve Insulin Signaling in Human Hepatocellular Carcinoma Cells

Marine natural products constitute a great source of potential new antidiabetic drugs. The aim of this study was to evaluate the role of phosphoeleganin (PE), a polyketide purified from the Mediterranean ascidian Sidnyum elegans, and its derivatives PE/2 and PE/3 on insulin sensitivity in human hepatocellular carcinoma (HepG2) cells. In our experiments, insulin stimulates the phosphorylation of its receptor (INSR) and AKT by 1.5- and 3.5-fold, respectively, whereas in the presence of PE, PE/2, and PE/3, the insulin induced INSR phosphorylation is increased by 2.1-, 2-, and 1.5-fold and AKT phosphorylation by 7.1-, 6.0-, and 5.1-fold, respectively. Interestingly, PE and PE/2 have an additive effect on insulin-mediated reduction of phosphoenolpyruvate carboxykinase (PEPCK) expression. Finally, PE and PE/2, but not PE/3, decrease interleukin 6 (IL6) secretion and expression before and after palmitic acid incubation, while in the presence of high glucose (HG), only PE reduces IL6. Levels of other cytokines are not significantly affected by PE and its derivates. All these data suggest that PE and its synthetic-derived compound, PE/2, significantly decrease IL6 and improve hepatic insulin signaling. As IL6 impairs insulin action, it could be hypothesized that PE and PE/2, by inhibiting IL6, may improve the hepatic insulin pathway.

Searching for Novel Sources of Hydrogen Sulfide Donors: Chemical Profiling of Polycarpa aurata Extract and Evaluation of the Anti-Inflammatory Effects

Hydrogen sulfide (H2S) is a signaling molecule endogenously produced within mammals' cells that plays an important role in inflammation, exerting anti-inflammatory effects. In this view, the research has shown a growing interest in identifying natural H2S donors. Herein, for the first time, the potential of marine extract as a source of H2S-releasing agents has been explored. Different fractions obtained by the Indonesian ascidian Polycarpa aurata were evaluated for their ability to release H2S in solution. The main components of the most active fraction were then characterized by liquid chromatography-high-resolution mass spectrometry (LC-HRMS) and NMR spectroscopy. The ability of this fraction to release H2S was evaluated in a cell-free assay and J774 macrophages by a fluorimetric method, and its anti-inflammatory activity was evaluated in vitro and in vivo by using carrageenan-induced mouse paw edema. The anti-inflammatory effects were assessed by inhibiting the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX2), and interleukin-6 (IL-6), coupled with a reduction in nitric oxide (NO) and IL-6 levels. Thus, this study defines the first example of a marine source able to inhibit inflammatory responses in vivo through the release of H2S.

Natural Bioactive Compounds from Marine Invertebrates That Modulate Key Targets Implicated in the Onset of Type 2 Diabetes Mellitus (T2DM) and Its Complications

BACKGROUND

Type 2 diabetes mellitus (T2DM) is an ongoing, risky, and costly health problem that therefore always requires new treatment options. Moreover, although several drugs are available, only 36% of patients achieve glycaemic control, and patient adherence is a major obstacle. With monotherapy, T2DM and its comorbidities/complications often cannot be managed, and the concurrent administration of several hypoglycaemic drugs is required, which increases the risk of side effects. In fact, despite the efficacy of the drugs currently on the market, they generally come with serious side effects. Therefore, scientific research must always be active in the discovery of new therapeutic agents.

DISCUSSION

The present review highlights some of the recent discoveries regarding marine natural products that can modulate the various targets that have been identified as crucial in the establishment of T2DM disease and its complications, with a focus on the compounds isolated from marine invertebrates. The activities of these metabolites are illustrated and discussed.

OBJECTIVES

The paper aims to capture the relevant evidence of the great chemical diversity of marine natural products as a key tool that can advance understanding in the T2DM research field, as well as in antidiabetic drug discovery. The variety of chemical scaffolds highlighted by the natural hits provides not only a source of chemical probes for the study of specific targets involved in the onset of T2DM, but is also a helpful tool for the development of drugs that are capable of acting via novel mechanisms. Thus, it lays the foundation for the design of multiple ligands that can overcome the drawbacks of polypharmacology.

Designed multiple ligands for the treatment of type 2 diabetes mellitus and its complications: Discovery of (5-arylidene-4-oxo-2-thioxothiazolidin-3-yl)alkanoic acids active as novel dual-targeted PTP1B/AKR1B1 inhibitors

Type 2 diabetes mellitus (T2DM) is a serious chronic disease with an alarmingly growing worldwide prevalence. Current treatment of T2DM mainly relies on drug combinations in order to control blood glucose levels and consequently prevent the onset of hyperglycaemia-related complications. The development of multiple-targeted drugs recently emerged as an attractive alternative to drug combinations for the treatment of complex diseases with multifactorial pathogenesis, such as T2DM. Protein tyrosine phosphatase 1B (PTP1B) and aldose reductase (AKR1B1) are two enzymes crucially involved in the development of T2DM and its chronic complications and, therefore, dual inhibitors targeted to both these enzymes could provide novel agents for the treatment of this complex pathological condition. In continuing our search for dual-targeted PTP1B/AKR1B1 inhibitors, we designed new (5-arylidene-4-oxo-2-thioxothiazolidin-3-yl)alkanoic acids. Among them, 3-(4-phenylbutoxy)benzylidene derivatives 6f and 7f, endowed with interesting inhibitory activity against both targets, proved to control specific cellular pathways implicated in the development of T2DM and related complications.

Marine natural products

Covering: January to December 2021This review covers the literature published in 2021 for marine natural products (MNPs), with 736 citations (724 for the period January to December 2021) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1425 in 416 papers for 2021), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of the number of authors, their affiliations, domestic and international collection locations, focus of MNP studies, citation metrics and journal choices is discussed.

Evidence of Insulin-Sensitizing and Mimetic Activity of the Sesquiterpene Quinone Avarone, a Protein Tyrosine Phosphatase 1B and Aldose Reductase Dual Targeting Agent from the Marine Sponge Dysidea avara

Type 2 diabetes mellitus (T2DM) is a complex disease characterized by impaired glucose homeostasis and serious long-term complications. First-line therapeutic options for T2DM treatment are monodrug therapies, often replaced by multidrug therapies to ensure that non-responding patients maintain target glycemia levels. The use of multitarget drugs instead of mono- or multidrug therapies has been emerging as a main strategy to treat multifactorial diseases, including T2DM. Therefore, modern drug discovery in its early stages aims to identify potential modulators for multiple targets; for this purpose, exploration of the chemical space of natural products represents a powerful tool. Our study demonstrates that avarone, a sesquiterpene quinone obtained from the sponge Dysidea avara, is capable of inhibiting in vitro PTP1B, the main negative regulator of the insulin receptor, while it improves insulin sensitivity, and mitochondria activity in C2C12 cells. We observe that when avarone is administered alone, it acts as an insulin-mimetic agent. In addition, we show that avarone acts as a tight binding inhibitor of aldose reductase (AKR1B1), the enzyme involved in the development of diabetic complications. Overall, avarone could be proposed as a novel natural hit to be developed as a multitarget drug for diabetes and its pathological complications.

Molecular and Biological Investigation of Isolated Marine Fungal Metabolites as Anticancer Agents: A Multi-Target Approach

Cancer is the leading cause of death globally, with an increasing number of cases being annually reported. Nature-derived metabolites have been widely studied for their potential programmed necrosis, cytotoxicity, and anti-proliferation leading to enrichment for the modern medicine, particularly within the last couple of decades. At a more rapid pace, the concept of multi-target agents has evolved from being an innovative approach into a regular drug development procedure for hampering the multi-fashioned pathophysiology and high-resistance nature of cancer cells. With the advent of the Red Sea Penicillium chrysogenum strain S003-isolated indole-based alkaloids, we thoroughly investigated the molecular aspects for three major metabolites: meleagrin (MEL), roquefortine C (ROC), and isoroquefortine C (ISO) against three cancer-associated biological targets Cdc-25A, PTP-1B, and c-Met kinase. The study presented, for the first time, the detailed molecular insights and near-physiological affinity for these marine indole alkaloids against the assign targets through molecular docking-coupled all-atom dynamic simulation analysis. Findings highlighted the superiority of MEL's binding affinity/stability being quite in concordance with the in vitro anticancer activity profile conducted via sulforhodamine B bioassay on different cancerous cell lines reaching down to low micromolar or even nanomolar potencies. The advent of lengthy structural topologies via the metabolites' extended tetracyclic cores and aromatic imidazole arm permitted multi-pocket accommodation addressing the selectivity concerns. Additionally, the presence decorating polar functionalities on the core hydrophobic tetracyclic ring contributed compound's pharmacodynamic preferentiality. Introducing ionizable functionality with more lipophilic characters was highlighted to improve binding affinities which was also in concordance with the conducted drug-likeness/pharmacokinetic profiling for obtaining a balanced pharmacokinetic/dynamic profile. Our study adds to the knowledge regarding drug development and optimization of marine-isolated indole-based alkaloids for future iterative synthesis and pre-clinical investigations as multi-target anticancer agents.

Identifying Human PTP1B Enzyme Inhibitors from Marine Natural Products: Perspectives for Developing of Novel Insulin-Mimetic Drugs

Diabetes mellitus (DM) represents a complex and multifactorial disease that causes metabolic disorders with acute and long-term serious complications. The onset of DM, with over 90% of cases of diabetes classified as type 2, implies several metabolic dysfunctions leading to consider DM a worldwide health problem. In this frame, protein tyrosine phosphatase 1B (PTP1B) and aldose reductase (AR) are two emerging targets involved in the development of type 2 diabetes mellitus (T2DM) and its chronic complications. Herein, we employed a marine-derived dual type inhibitor of these enzymes, phosphoeleganin, as chemical starting point to perform a fragment-based process in search for new inhibitors. Phosphoeleganin was both disassembled by its oxidative cleavage and used as model structure for the synthesis of a small library of functionalized derivatives as rationally designed analogues. Pharmacological screening supported by in silico docking analysis outlined the mechanism of action against PTP1B exerted by a phosphorylated fragment and a synthetic simplified analogue, which represent the most potent inhibitors in the library.

Insights into Cytotoxic Behavior of Lepadins and Structure Elucidation of the New Alkaloid Lepadin L from the Mediterranean Ascidian Clavelina lepadiformis

The chemical investigation of the Mediterranean ascidian Clavelina lepadiformis has led to the isolation of a new lepadin, named lepadin L, and two known metabolites belonging to the same family, lepadins A and B. The planar structure and relative configuration of the decahydroquinoline ring of lepadin L were established both by means of HR-ESIMS and by a detailed as extensive analysis of 1D and 2D NMR spectra. Moreover, microscale derivatization of the new alkaloid lepadin L was performed to assess the relative configuration of the functionalized alkyl side chain. Lepadins A, B, and L were tested for their cytotoxic activity on a panel of cancer cell lines (human melanoma [A375], human breast [MDA-MB-468], human colon adenocarcinoma [HT29], human colorectal carcinoma [HCT116], and mouse myoblast [C2C12]). Interestingly, a deeper investigation into the mechanism of action of the most cytotoxic metabolite, lepadin A, on the A375 cells has highlighted its ability to induce a strongly inhibition of cell migration, G2/M phase cell cycle arrest and a dose-dependent decrease of cell clonogenity, suggesting that it is able to impair self-renewing capacity of A375 cells.